<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>promise的all方法</title>
</head>
<body>
    
</body>
<script>
    //promise.all()将多个promise示例合并成一个新实例
    // 只有所有的promise实例的状态都为fulfilled，最终结果才能执行.then
    // 如果有一个promise实例的状态为rejected，那么最终结果会执行.catch
    let promise1 = new Promise((resolve,reject)=>{
        setTimeout(()=>{
            resolve(1000)
        },1000)
    })

    let promise2 = new Promise((resolve,reject)=>{
        setTimeout(()=>{
            resolve('hello')
        },1000)
    })

    let promise3 = new Promise((resolve,reject)=>{
        setTimeout(()=>{
            reject('promise3失败了')
        },1000)
    })

    let promise4 = Promise.all([promise1,promise2,promise3])
    .then((res)=>{
        console.log(res);

    })
    .catch((err)=>{
        console.log(err);
    })
</script>
</html>